Slaughter was also down 4% on the month last year, to 21 million head.
The incident took place in the Lviv region, on a large farm owned by Halychyna Zahid company.
The number of sows has also dropped by 31.9% due to ASF crisis in the country.
The country's herd of 616,000 head may be at risk due to ASF outbreaks.
Exports are expecting a second wave of high volume of pork to enter the country.
In the year to May, imports of pig meat increased by over 50% on the year.
Piglet prices have spiked by 3/4 in one year to reach €35 in the Spanish market.
9 Italian slaughterhouses are allowed to export frozen pork and offals to China.
The ongoing ASF outbreaks in the country may reduce the national pig inventory by 20%.
